1. Field of the Invention
The present invention relates to a weft cutter device for an air loom, which weft cutter, while being inexpensive, compact, operationally reliable and structurally simple, makes it possible for the cutting times to be promptly and directly controlled as a function of the weaving conditions and, above all, the cutting operation to be disabled at will, even while the loom is operating.
2. Discussion of the Background
It is well-known that in an air weaving loom the weft thread, drawn from a cop external to the loom, is entered into the open shed formed by the warp threads, from a plurality of nozzles and only after said warp threads have reversed the shed by mutually exchanging their position, so as to lock the inserted weft thread between them, said weft thread is cut by the weft cutting device, so as to disengage it from said cop.
According to the prior art, the weft cutter used is substantially constituted by a stationary blade with which a movable blade cooperates, by being caused to oscillate by a mechanical drive means of a cam type.
Unfortunately, besides not allowing a direct and fast selection of the cutting times without having to act on in the loom, because such a selection would require a manual action being performed inside the interior of the loom in order to disengage the fastening means of said cam onto its own shaft in order to suitably rotate said cam by a certain angle and finally to engage again said lock system, such a device known from the prior art does not even allow the cutting operation to be disabled during loom operation.
In order to obviate said drawbacks, said oscillation of the movable cam was accomplished by means of an electro-mechanical drive unit in which a stepper motor drives the motion of the movable blade through a suitable kinematic link means, or an electromagnetic drive means in which the movable blade is driven by the action of an electromagnet.
In fact, in these cases, the possibility is evident of selecting the cutting times and of disabling said cutting action at will, by suitably offsetting in time, or completely removing the motor or electromagnet biasing command. However, this latter type of weft cutters known from the prior art are affected by structural complexities which cause them to be rather expensive.